Method and System for Scheduling Utilization of Resources, Related Communication Network and Computer Program Product

1. A method of scheduling utilization of a service resource by a plurality of flows of information packets, said plurality of flows comprising rate-guaranteed synchronous flows and best-efforts asynchronous flows, wherein said asynchronous flows exploit the service capacity of said resource left unexploited by said synchronous flows, comprising the steps of: providing a server that visits said plurality of flows in subsequent rounds, said server visiting first within each said round said synchronous flows followed by said asynchronous flows; detecting any backlogged synchronous flow in said plurality of synchronous flows; when said server visits any said backlogged synchronous flow, allowing said backlogged synchronous flow to utilize said resource for a given time, whereby said synchronous flows have a guaranteed transmission window on each said round; determining a reference round time indicative of the expected time for said server to complete a round of visits of said plurality of flows; when said server visits any said asynchronous flow, determining the time elapsed since the last visit by said server to the same asynchronous flow; and: i) if the visit to said asynchronous flow occurs later than expected based on said reference round time, restraining said asynchronous flow being visited from utilizing said resource for the ongoing round, ii) if the visit to said asynchronous flow occurs earlier than expected based on said reference round time, allowing said asynchronous flow being visited to utilize said resource for a respective given time, said respective given time being a function of an earliness value representing an amount of time the server visit is earlier than expected, whereby said function regulates the exploitation by each said asynchronous flows of said service capacity of said resource left unexploited by said synchronous flows, wherein said respective given time is proportional to said earliness value via a proportionality factor, and wherein said proportionality factor is a ratio of a weight assigned to said asynchronous flow to a maximum weight among a plurality of weights assigned to said asynchronous flows.

2. The method of claim 1 , wherein said server stops visiting any said flows, when said given time or respective given time has elapsed, or when the flow being visited has cleared its backlog, whichever occurs first.

3. The method of claim 1 , comprising the steps of: determining a synchronous bandwidth for said synchronous flows; and setting an upper bound to said given time as a function of said synchronous bandwidth.

4. The method of claim 1 , comprising the steps of: associating with each said asynchronous flow a value indicative of delay accumulated by said server in visiting said asynchronous flow in previous rounds; when said server visits said asynchronous flow, subtracting from said reference round time a duration of a previous round to obtain a subtraction result; and subtracting said value from said subtraction result thus computing said earliness value for a current round.

5. The method of claim 4 , comprising the steps of: if said earliness value is negative, storing an absolute value thereof in said value indicative of delay accumulated; and restraining said asynchronous flow being visited from utilizing said resource for said current round.

6. The method of claim 4 , comprising the steps of: if said earliness value is positive, resetting to zero said value indicative of delay accumulated; and granting said asynchronous flow being visited said respective given time for utilizing said resource.

7. The method of claim 1 , comprising the step of selecting said proportionality factor in a range (0,1].

8. The method of claim 1 , comprising the step of selecting respective proportionality factors for said asynchronous flows.

9. The method of claim 1 , comprising the step of determining respective synchronous bandwidths for said synchronous flows, wherein a sum of time intervals corresponding to said synchronous bandwidths is lower than or equal to said reference round time.

10. A system for scheduling utilization of a service resource by a plurality of flows of information packets, said plurality of flows comprising rate-guaranteed synchronous flows and best-effort asynchronous flows, wherein said asynchronous flows exploit the service capacity of said resource left unexploited by said synchronous flows, the system comprising a server configured for visiting said plurality of flows in subsequent rounds, said server visiting first within each said round said synchronous flows followed by said asynchronous flows, said server being configured for: detecting any backlogged synchronous flow in said plurality of synchronous flows, when said server visits any said backlogged synchronous flow, allowing said backlogged synchronous flow to utilize said resource for a given time, whereby said synchronous flows have a guaranteed transmission window on each said round; determining a reference round time indicative of the expected time for said server to complete a round of visits of said plurality of flows, when said server visits any said asynchronous flow, determining the time elapsed since the last visit by said server to the same asynchronous flow, and: i) if the visit to said asynchronous flow occurs later than expected based on said reference round time, restraining said asynchronous flow being visited from utilizing said resource for the ongoing round, ii) if the visit to said asynchronous flow occurs earlier than expected based on said reference round time, allowing said asynchronous flow being visited to utilize said resource for a respective given time, said respective given time being a function of an earliness value representing an amount of time the server visit is earlier than expected, whereby said function regulates the exploitation by each said asynchronous flows of said service capacity of said resource left unexploited by said synchronous flows, wherein said respective given time is proportional to said earliness value via a proportionality factor, and wherein said proportionality factor is a ratio of a weight assigned to said asynchronous flow to a maximum weight among a plurality of weights assigned to said asynchronous flows.

11. The system of claim 10 , wherein said server is configured for stopping visiting any said flows: when said given time or respective given time has elapsed, or when the flow being visited has cleared its backlog, whichever occurs first.

12. The system of claim 10 , wherein said sever is configured for: determining a synchronous bandwidth for said synchronous flows; and setting an upper bound to said given time as a function of said synchronous bandwidth.

13. The system of claim 10 , wherein said server is configured for: associating with each said asynchronous flow a value indicative of delay accumulated by said server in visiting said asynchronous flow in previous rounds, when said server visits said asynchronous flow, subtracting from said reference round time a duration of a previous round to obtain a subtraction result, and subtracting said value from said subtraction result, thus computing said earliness value for a current round.

14. The system of claim 13 , wherein said server is configured for: if said earliness value is negative, storing an absolute value thereof in said value indicative of delay accumulated; and restraining said asynchronous flow being visited from utilizing said resource for said current round.

15. The system of claim 13 , wherein said server is configured for: if said earliness value is positive, resetting to zero said value indicative of delay accumulated; and granting said asynchronous flow being visited said respective given time for utilizing said resource.

16. The system of claim 10 , wherein said server is configured for using as said proportionality factors in a range (0,1].

17. The system of claim 10 , wherein said server is configured for using respective proportionality factors for said asynchronous flows.

18. The system of claim 10 , wherein said server is configured for determining respective synchronous bandwidths for said synchronous flows, wherein a sum of time intervals corresponding to said synchronous bandwidths is lower than or equal to said reference round time.

19. A communication network comprising the system of claim 10 .

20. A non-transitory computer readable medium encoded with a computer program product loadable into a memory of at least one computer and comprising software code portions for performing the method of claim 1 .